III. Causes of Current Mass Extinction H - Habitat Destruction and Fragmentation I - Invasive species P - Pollution P - Population O - Overharvesting

1. Habitat Destruction – complete change in ecosystem type: Ex.: 1960 – 1990, Tropical Rainforests in Central America 40% destroyed by slash-and-burn agriculture followed by cattle pasture

1. Habitat Destruction Ex.: clear cutting of forest

1. Habitat Destruction Ex. clear cutting of forest Ex. conversion of grasslands to crop fields

Fragmentation chops habitat into small unconnected pieces

Fragmentation is a problem because: -less food -less area means smaller population -some species require large territories Borneo

Fragmentation is a problem because: -it divides populations into isolated groups → issues finding a mate → less genetic diversity

Fragmentation is a problem because: -it creates edges between two habitat types Edges are a blend of two habitat types Good areas for generalists who can survive in many places

Edges - Not good for specialists Need large tracts of grasslands in NH

Which of the following is NOT an issue associated with habitat fragmentation 1.Edges 2.Isolated populations 3.Decrease in amount of food available 4.Increase in top predators

2. Introduction of Exotic Species are species that evolved elsewhere Most are not a problem Some become invasive – out-compete native species Purple Loosestrife Asian Longhorn Beetle

Some become invasive – out-compete native species Have no natural predators Native species have no defenses Ex. Brown tree snake in Guam, caused extinction of almost all native forest birds, reptiles and small mammals

3. Pollution decreases the quality of the habitat Ex. Deaths of 1,000s of seals believed to be linked to pollution such as DDT, PCBS and dioxins

Ex. Waterfowl ingest shotgun pellets which stay in their gizzards → lead poisoning Ex. Common Loon

4. Population (Human) – Our activities are negatively impacting the environment As human pop grows – greater impact on the environment

5. Overharvesting – Hunting, harvesting or removing animals and plants faster than they reproduce Ex. Passenger pigeon 1813: 2 billion 1914: Extinct

5. Overharvesting – Hunting, harvesting or removing animals and plants faster than they reproduce Ex. American Bison Almost hunted to extinction

An exotic species is best defined as 1.A very competitive species 2.A species that evolved somewhere else 3.A species successful at reproducing 4.A species that causes other species in the ecosystem to go extinct

Small pop are at greater risk of extinction Random events such as a storm or fire may further decrease the population national geographic.com Komodo dragon Total Pop: ~5000 Breeding females: ~350

Fewer genetic differences means there is less ability to adapt to changes in the environment Inbreeding

–Increases offspring mortality –Decreases fertility –Reduces resistance to disease Ex. Cheetah

Inbreeding due to few individuals to mate with –Increases offspring mortality –Decreases fertility –Reduces resistance to disease These factors result in a smaller and smaller pop. = Extinction Vortex

IV. Saving Biodiversity In 1894 there were less than 300 American bison. Now there are 500,000

California Condor 1987: 27 in captivity STATUS 348 (48 more than last year!)

Peregrine Falcons 1970: Only 39 breeding pairs Today: 2,000 – 3,000 pairs